Question

Going for a long trip, Joshwa drove for 3 hours and had lunch. After lunch he drove for 4 more hours at a speed that is 10 km/h more than before lunch. The total trip was 600 km.
(a)​What was his speed before lunch?
(b)​What distance did he drive after lunch?

Answer 1

Answer :

we know Speed = $\frac{Dis\tan ce}{Time}$
Let
Joshwa's Speed before lunch = x km /hr
And
Joshwa's Cover total distance before lunch = y km
And
Given : Joshwa drove for 3 hours before lunch ,

SO

x = $\frac{y}{3}$

y = 3x ------------ ( 1 )
And
After lunch he drove for 4 more hours at a speed that is 10 km/h more than before lunch.
So,
Speed after lunch = x + 10 km /hr

Given Total trip was 600 km , So

Distance travel after lunch = 600 - y

Then we get

x + 10 = $\frac{600-y}{4}$

4x + 40 = 600 - y

4x + y = 560 , Substitute value from equation 1 , we get

4x + 3x = 560

7x = 560

x = 80

So,

a ) Speed before lunch = 80 km/hr ( Ans )

b ) We know Speed before lunch = 80 km/hr , Joshwa drove for 3 hours before lunch
So,
Total distance cover by joshwa before lunch = 80 $\times$ 3 = 240 km
So,
Total distance Joshwa drove after lunch = 600 - 240 = 360 km ( Ans )